1. Field of the Invention
The present invention relates to the improvement in an information input display device, which comprises a display mounted on an information terminal represented by a portable telephone or PDA (personal digital assistant) and an input section disposed on the display.
2. Description of the Related Art
An information terminal having a liquid crystal display for displaying information are generally known. On the liquid crystal display, there is provided a device mounted with a touch panel serving as an input section. Through the input section, instructions to select display items, or input of characters, numerals, etc. can be carried out by touching the touch panel so as to put pressure thereon.
The touch panel generally has a structure as shown in FIG. 9. In the touch panel 1, a conductive layer 102 is formed on a glass substrate 101 (or a plastic substrate) by using a technique of forming layer such as a vapor deposition method, and wiring 103 made of material having low resistivity such as silver (Ag) etc. is formed on the conductive layer 102. The glass substrate 101 with insulating properties is transparent or capable of display in a transmittable manner. Separately from the above, coating layers 105 are formed on both surfaces of a film 104 so as to make the film 104 durable. The film 104 is made of a PET (polyethylene terephthalate) sheet etc. and transparent or capable of display in a transmittable manner. A conductive layer 106 is formed on one of the coating layers 105.
A surface of the glass substrate 101 on which conductive layer 102 is formed and a surface of the film 104 on which the conductive layer 106 is formed are opposed to each other, and both peripheral end portions of the above surfaces are bonded together with a space of about 0.1 mm interposed therebetween with an adhesive 107 such as a adhesives double sided tape etc. In such a structure, by putting pressure on the film 104 from above, the conductive layer 106 is brought into contact with the conductive layer 102, thereby input can be carried out.
Being manufactured for portable use, this information terminal is miniaturized and lightened. Therefore, a user can carry the terminal in bag or a pocket. Naturally enough, the information terminal may be dropped mistakenly while the user is carrying it with him or her, or holding it in his or her hand. So, measures to relieve impact caused by being dropped have been taken to the terminal, so as to prevent it from being damaged. With respect to the display section including the touch panel, an elastic member such as rubber etc. surrounds an edge of the display section to protect the display from an impact and from water damage. In addition, preventive measures against damage caused by static electricity are also taken. For example, as such a structure, the present applicant has disclosed a constitution as shown in FIG. 10 to realize the moderation of impact and waterproofing.
FIG. 10 is a cross-section view of a device, wherein a touch panel 109 is superposed with a liquid crystal display (not shown), and a gasket 108 with a hook-shaped cross-section, which has elasticity and thus can be a buffer, is fitted in a manner of surrounding an edge of the superposed touch panel 109 and liquid crystal display around. The superposed touch panel 109 and liquid crystal display is fixed by means of a metal frame (not shown) so as to support and press the gasket 108 against a housing 110. In such a structure, as shown in FIG. 10, an end portion of the gasket 108, which comes into contact with the touch panel 109, is formed into a ring shape. When the gasket 108 is pressed by the metal frame (not shown), the end portion of the gasket 108 is crushed between a surface of the touch panel 109 and an inner surface of the housing 110. Thus, the touch panel 109 can be held and fixed with proper force, while having a waterproof function.
In the aforementioned touch panel, a case may occur in that the film 104 constituting a surface of the panel is swelled or corrugated owing to deterioration with lapse of time, temperature or humidity. In the touch panel, the almost entire periphery of the film 104 is bonded to the glass substrate 101 with the adhesive 107 so that the film 104 is fixed. There is a difference in the coefficient of thermal expansion or elongation caused by moisture absorption between the film 104 and the glass substrate 101. Therefore, the swell or corrugation may occur easily owing to the influence of heat or humidity, or deformation of the adhesive 107 owing to heat.
In the case where the film 104 is swelled or corrugated as having previously been described, a problem arises in that: even if input operation is performed by signing with light force, the operation can not be carried out properly; or input operation can not be performed because of a short-circuit between the conductive layer 106 of the film 104 and the conductive layer 102 on the glass substrate 101. In addition, when the distance between the film 104 and the glass substrate 101 becomes considerably short, another problem thus arises in that Newton ring occurs so that it becomes difficult to see information displayed on the panel.
This touch panel is seldom used alone. In general, the touch panel is disposed on a display screen and incorporated in a device for use. If the aforementioned information terminal mounted with the touch panel is for industrial use, the touch panel is to be used under severe conditions (for example, the operation environment is in the range of −20 to 50° C., the storage environment is in the range of −40 to 70° C.). For this reason, it is required for the touch panel to have excellent durability.
A touch panel (information input device) to be mounted on an information terminal shown in FIG. 10 is fixed through the gasket 108 so as to provide protection from impact and water. In a structure in which the gasket 108 surrounds the touch panel 109 as shown in FIG. 10, assume that the film 104 of the touch panel 109 elongates owing to high temperature or moisture absorption. In this case, even if the temperature or humidity has fallen and thus a portion of the film, which is drawn to the inner side from the point where the gasket holds the film down, is intended to revert to its former state, it cannot be achieved owing to the pressure from the gasket. The portion remains on the display screen so that swelling or corrugation may occur.
In addition to such a phenomenon, assume a state in which the touch panel moves in assembly to the housing 110 or after shipment, and the gasket 108 holds an end portion of the touch panel 109 as shown in FIG. 11. In such a state, the force (denoted by a reference character Fe in FIG. 11) to intend the film 104 to move to the inner side occurs, and thus an adhered portion is displaced to the inner side. Therefore, the film is swelled or corrugated. In addition, as the degree of crushing an end portion of the gasket 108 is increased so as to hold the film 104 harder for the purpose to waterproof the device or prevent the touch panel 109 from being moved, swelling or corrugation appears remarkably and easily. When the swelling or corrugation occurs of the film, a problem similar to ones described above arises.